I have recently bought a pre-64 model 70 in .264. I took it to the range for the first time today to shoot. Got it sighted in and shot a 1-1/4" group with Winchester ammo. Switched to Hornady Supreme and with the first shot, the bolt will not open. It will lift about 1/2" and that's it. If anyone has any idea what I can try, I'd appreciate it. Otherwise I'll be visiting a gunsmith this week. Thanks.